1. Field of the Invention
The present invention relates to a data processing apparatus for processing data relating to image output.
2. Related Background Art
A typical example of output apparatus equipped with data processing apparatus is a laser beam printer. In such laser beam printer, image data based on input print data (image data or character codes) are developed in succession in an internal image memory.
If the data are entered overflowing the area of the printing medium (printing sheet) in such image data development, such overflowing data are normally discarded or developed in a succeeding print medium.
Thus, the output result intended by the operator cannot be obtained when such overflowing part is present.
In order to avoid such situation, it becomes necessary to process or edit such print data in the data source (host computer) so as that said data can be accommodated within the printing medium, but such processing after the data are once prepared or edited is cumbersome and inefficient.
Also in such conventional apparatus, character patterns are generated corresponding to character codes, by analyzing the control code data (command codes) in the print data from the host computer or the like and referring to a character font ROM incorporated in the apparatus or connected thereto, based on the kind, style and size of the character. The character patterns thus obtained are developed for example in corresponding positions of a bit map memory for printing. However, in case of enlarged or reduced printing of a page, the character size and printing pitch in the print command supplied from the host computer have to be varied. Thus the host computer has to supply different command data to the printing unit by re-editing the output, and the burden to the operator is significant.
Also if the editing software of the host computer has fixed size and pitch of the characters and is unable to select said size or pitch, the enlargement or reduction of each page has been not possible.
As explained above, the printing apparatus executes printing operation by receiving character codes from an external host computer (including a word processor a personal computer) and generating character patterns by a character font ROM provided in said apparatus.
Particularly in case of a page printer for receiving and printing the print data in the unit of a page, character patterns corresponding to the input character codes are developed, in the unit of a page, on the memory according to the instructed print position, style, size, character pitch and line pitch, then edited and printed by a printing mechanism.
However, even if the print data from the host computer are not final and merely for the confirmation of content, it is necessary to follow the same printing procedure.
For example if the data to be printed are a program list under development and subject to changes and are large in quantity, the printing of all these data on successive pages not only leads to the waste of printing sheets but also the time required for the entire printing.
Also in the above-mentioned page printers for editing the print data supplied from a data source such as a host computer into a page and printing said print data, there is already known a laser beam printer in which a laser beam modulated by the print data such as characters or image data is directed to a polygon mirror rotating at a high speed and an electrostatic latent image is thereby formed on a photosensitive member.
However, in certain page printers, the effective printing area is determined in advance, and the printer calculates the number of characters printed in the horizontal direction so as to effect the printing in a range corresponding to the sizes (B4, A4) of the printing sheet. Thus, if the input print data contain a number of characters exceeding the above-mentioned calculated number of characters, the printing can only be made up to the A4-size even if said print data instruct the printing on a B4-sized sheet. In such printers, there may result a drawback that the obtained print lacks a part of the print data.
Also in such conventional printing apparatus, the printing operation is often not conducted if the quantity of the received print data is large, for example because said data overflows the printing sheet. In such case, there is usually given, from the data source, an instruction for printing with smaller characters, in order to increase the number of characters per unit area thereby accommodating the print data within the desired printing sheet.
However, in such case, the operator is required to conduct cumbersome operations of selecting the character pitch and line pitch.
Also the use of smaller characters may result in more blinded print then anticipated.
Furthermore, the above-mentioned page printers are so designed as to print, with high quality, the print data containing characters and images, prepared by image editing achieved in so-called desktop publishing.
It is also possible to print text data with a desired size, by suitably selecting character patterns of different dot numbers stored in the apparatus in advance.
However, if the sheets of a size designated by the host computer are not loaded in the apparatus, the printing operation is interrupted by terminating the data reception after a command designating said sheet size.
In such case, therefore, it is necessary to vary the format of the print data in the host computer, or to replace the printing sheets loaded in the printing apparatus.
Furthermore, an assignee of the present application has some patents associated with various data processing apparatus, for example, the U.S. Pat. Nos. 4,059,833, 4,107,786, 4,393,387, 4,686,525 and 4,715,006, but further improvements have been longed for.